75-14-02: Rotor Hub Quadruple Nuts

75-14-02 MESSERSCHMITT BOELKOW BLOHM GMBH: Amendment 39-2246. Applies to Messerschmitt Boelkow Blohm (MBB) Model BO-105 Helicopters certificated in all categories. Compliance is required as indicated. To prevent failure in service of certain main rotor hub quadruple nuts due to cracks resulting from manufacturing defects, accomplish the following: (a) Within the next twenty hours time in service after the effective date of this AD, determine the production lot number of the two installed main rotor hub quadruple nuts, P/N 105- 14101.19 and .20. NOTE: Quadruple nuts are identified "VIERFACHNUSS" on P/N drawings. Production lot number of nuts is set forth as first two digits of serial number recorded in MBB individual aircraft historical record document, under the heading of Main Rotor Head Assembly No. 105-14101. (b) If the lot number determined in accordance with paragraph (a) of this AD is 06 or 07, or if the lot number cannot be determined, before further flight, except that the aircraft may be flown in accordance with FAR Section 21.197 and 21.199 to a base where the work can be performed, remove the two quadruple nuts and replace with serviceable parts of the same part number. (Messerschmitt Boelkow Blohn BO-105 Alert Service Bulletin No. 9 covers this same subject). This amendment is effective upon publication in the Federal Register as to all persons except those persons to whom it was made immediately effective by the telegram dated May 14, 1975, which contained this amendment.